Patent Document 1 discloses a method of sealing a pipe joint in which a plate-like metal sealing member is interposed and secured between two metal pipe members. In this sealing method, by welding the two metal pipe members in an area ensuring that heat applied in welding does not influence the metal sealing member, a weld contracting in a direction causing the metal sealing member to be secured between the two pipe members is formed. As a result of deformation of the metal pipe members caused by the contraction of the weld, the sealing member is secured, and thus, air-tightly held between the two metal pipe members.